Characterisation of Cannabis glandular trichome development reveals distinct features of cannabinoid biosynthesis

Cannabis trichome development progresses in distinct phases that underpin the dynamic biosynthesis of cannabinoids and terpenes. This study investigates the molecular mechanisms underlying cannabinoid and terpenoid biosynthesis in glandular trichomes of Cannabis sativa (CsGTs) throughout their development. Female Cannabis sativa c. Hindu Kush were cultivated under controlled conditions, and trichome development was analysed from week 3 to week 8 of the flowering period. We employed light microscopy, quantitative metabolomics and proteomics to analyse morphological changes in trichome secretory cell development, and temporal changes in metabolite accumulation and protein abundance. Our findings identified three distinct developmental phases: pre-secretory (T3), secretory (T6), and post-secretory (T8), the first time the three phases of trichome development have been identified and investigated in CsGTs. The pre-secretory phase was characterized by smaller secretory cells, limited metabolite accumulation and elevated levels of proteins involved in protein biosynthesis and cellular development. The secretory phase exhibited the highest biosynthetic activity, marked by larger secretory cells, increased plastidal activity, central carbon metabolism, and significant accumulation of cannabinoids and terpenoids. The post-secretory phase showed a decrease in secretory cell size, reduced metabolic activity, and a decrease in the abundance of primary and secondary metabolism enzymes, although THCA continued to accumulate. Key enzymes showed dynamic changes correlating with the stages of trichome development. This study provides a comprehensive understanding of the molecular mechanisms regulating cannabinoid and terpenoid biosynthesis in CsGTs, offering insights for enhancing the production of these valuable compounds through targeted breeding and biotechnological approaches.